A known method for manufacturing stators for pumps or motors with eccentric shafts comprises, for example, manufacture by means of non-cutting formation of stators, and thus of their interior stator work face, from elastic rubber or from plastic. However, stators resulting from such manufacturing processes have the disadvantage that in practice they can only be used within a limited temperature range, the respective temperature range being determined by the plastic material from which they are molded.
Additionally, methods for manufacturing stators are known which make use of machining techniques, so that it is possible to manufacture stators, which are to be installed in particular in pumps or motors, which are usable at higher working temperatures.
Such known machining methods comprise, for example, so-called interior-off-center-contour-lathe methods, where the profile of the inner bore of the stator is created in the shape of interior, machined working surfaces, in particular with the aid of boring bars or turn-out rods. However, the working depth of such contour lathe methods is relatively limited, i.e. there is a length limitation for the resulting stators in accordance with the formula: EQU L.ltoreq.15 D
where L is the length of the stator profile and D the diameter of the profile of the inner bore.
Thus, the known contour lathe methods only permit the manufacture of inner bore profiles having only a comparatively limited length which, of course, is considered to be quite disadvantageous in practice. Other disadvantages are unfavorable cutting conditions, slow working speeds, irregular machining, etc.
To overcome these difficulties, it has already been attempted in accordance with the state of the art to manufacture stators made of several individual short longitudinal pieces and subsequently to put these separate longitudinal pieces axially together, because in practice there is often eccentric shaft pumps of active pump length which sometimes needs to be several meters in order to make it possible to satisfy the requirement for certain pumping or output parameters. In connection with such a manufacturing method there is, however, a serious problem with working the transition faces of the inner bore profile of the stator, since these transition faces are hardly accessible to tools. The result of this is inexact fit, which causes reductions in tool life and output.
In this connection the inner stator impact surfaces which must be worked are particularly hard to reach so that in cases where such stators are intended to be manufactured by means of the customary machining technology it would be required to put the stator together out of a large number of relatively thin disks where the inner impact surfaces can be worked relatively well. However, such a method is very inefficient in practice because, as a rule, a large number of single work pieces must be individually worked and then these single work pieces must be assembled.